Heat exchangers are used to transfer heat absorbed by a first fluid to a second cooling fluid. Either fluid may flow through passages located within the exchanger or around the passages, passing through openings extending through the exchanger that are spaced about the passages and are defined by a plurality of fins extending outwardly around the passages. Prior art heat exchangers have been constructed in a multitude of arrangements to expose the maximum surface area on the passages and the surrounding fins to allow the greatest heat transfer to occur between the first and second fluids.
Older heat exchangers consist of arrangements of tubular passages having radially extending fins spaced from one another and attached to the passages in a permanent relationship. Heat exchangers of this type, while effective in cooling the heated first fluid flowing from the engine, are difficult to maintain and repair due to the unitary construction of the heat exchanger, as this construction necessitates the total disassembly of the exchanger to repair the exchanger. Disassembling these types of exchangers requires that the permanent connections between the components of the heat exchanger be undone, a process which is both time consuming and expensive.
More recent developments with regard to fluid heat exchanger design have resulted in the creation of modular heat exchangers, such as that disclosed in U.S. Pat. No. 5,303,770. In this heat exchanger, the exchanger is comprised of a number of aluminum modules that are positioned against one another to form the modular heat exchanger. Each module disclosed in the above-identified patent consists of an elongate, rectangular extruded aluminum block including longitudinally extending oval-shaped passages and a series of outwardly extending fins spaced around the passages along the exterior of the block on the wide face thereof.
The modules are preferably welded together with end pieces or header plates formed of the same metal as the modules to insure weld integrity and to avoid potential problems of weld failure resulting from differential thermal expansion in dissimilar metals. Therefore, to avoid these problems, the inlet and outlet end pieces or header plates, as well as the accumulator tanks or any other attachments connected to the modular elements, should be formed of aluminum to insure that the welded connections will not fail. This necessarily limits the application of the modular heat exchanger comprised of the extruded aluminum block modules to uses in which any necessary attachments welded to the heat exchanger, and any other elements welded to those attachments, can be formed of the same metal as the exchanger elements.